During the early '90s -- nearly a full 20 years after punk happened -- the United States had its first punk rock hit albums and singles, as a wave of bands raised on '80s hardcore and '70s punk worked its way into the American mainstream. Essentially, Punk Revival bands were all traditionalists -- they kept alive the sounds and styles of groups like the Sex Pistols, the Stooges, the Jam, the Exploited, Black Flag, Dead Kennedys, the Descendents, and countless other punk and hardcore bands. Since hardcore mutated into speed metal in the late '80s, it wasn't surprising that these punk traditionalists were heavier than their initial influences, but that is partially what made the music appealing to a mass audience in America -- it was simpler and heavier, much like a faster, harder outgrowth of grunge rock. The first punk revivalists to break into the American mainstream were Green Day and the Offspring, and their success helped solidify cult followings for groups like Rancid, NOFX, Pennywise, and Pansy Division, as well as bring the spotlight to neglected '80s punk bands like Bad Religion and underground punk genres like the third wave of ska revival.